• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.10
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• pp.102-110
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• 2012

This paper propose the advanced topology of UPQC, its DC link is connected with Lithium battery, to compensate the momentary interruptions. The proposed system can be operated as UPS mode using the parallel inverter, which control the charge or discharge of battery, in case of the interruption. We dvelop 100kVA UPQC using the proposed topology to rise the power quality and the reliability of Microgrid. We verify its usefulness through voltage compensation test, UPS operation test and etc. using Microgrid test facility.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.487-490
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• 2001

Power Quality and Reliability are becoming important issues for critical and sensitive loads. This paper describes the Line Interactive UPS with the function of Voltage Compensator that is 'Line interactive Dynamic Voltage Restorer(LIDVR). The main purpose of a LIDVR is to compensate for voltage sag(dip), outage and overvoltage. The overall system consists of three controller 1) current controller with prediction 2) voltage controller and 3) proposed variable DC LINK controller. The variable DC LINK control technique using the LIDVR protects DC LINK from overflowing the input current. The simulation results are depicted in this paper to show the effect of this proposed system.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.298-299
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• 2010

In this paper a robust voltage controller of single-phase inverter for UPS is presented. The voltage controller is designed using ${\mu}-based$ robust control scheme to simultaneously guarantee robust stability and robust tracking performance in presence of filter and load parameter variations. Firstly the robust performance of the resulting controller is theoretically confirmed via ${\mu}-analysis$. Then simulation results for single-phase inverter system with linear and nonlinear loads demonstrate feasibility of the proposed control method providing improved performance - good regulation and fast dynamic response.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.11
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• pp.655-662
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• 1999

This paper describes controller design and simulation-model development of a dynamic voltage compensator using series and shunt inverters. The control system was designed using PI controller and vector relationship between the supply voltage and load voltage. A simulation model with EMTP was developed to analyze performance of the controller and the whole system. The simulation and experiment results confirm that the dynamic compensator can restore the load voltage under the fault of the distribution system, such as single-line-ground fault, three-line-to-ground fault, and line-to-line fault.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.5
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• pp.17-30
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• 2022

It has been verified in several studies that dynamic capabilities has a very important effect on the competitive advantage of technology startups. And the network has an important influence on this dynamic capability. This is even more important for start-ups that lack the resources and knowledge. Networks that directly and significantly affect dynamic capabilities have been studied mainly the value chain internal. However, network activities of start-ups are conducted not only with the value chain internal networks but also with the value chain external networks. Therefore, it is necessary to study the effect of the value chain internal and external network activity of start-ups on the dynamic capabilities, but prior studies are lacked. In this study, We make a model that encompass the value chain internal and external network for technology startups, and a study was conducted to demonstrate the effect on dynamic capabilities and competitive advantage. As a result of the study, value chain internal network activity directly and significantly affected dynamic capabilities, and value chain external network activity did not directly significantly affect dynamic capacity. And dynamic capabilities had a significant effect on competitive advantage. As confirmed through additional research, value chain external network activity affects value chain internal network activity, and through this, dynamic capabilities are strengthened, and positively affect competitive advantage.. The intensity of value chain external network activity was not significant to dynamic capabilities and the diversity of value chain external network activity had a significant effect on the competitive advantage by double mediating the value chain internal network activity and dynamic capability. Through this study, it is confirmed that the value chain internal networks is important in order for startups to strengthen their dynamic capabilities and increase their competitive advantage, and that both strong and diversified the value chain internal networks positively affects competitive advantage by enhancing dynamic capabilities.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1065-1070
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• 2006

The beam structure models with an impactor or contact parts under impact forces have teen applied to the design of mechanical and electronic accessories. Switches, hard-disk pick-ups and sensors are typical structural examples of the structure to be designed to colliding with other parts of structures. In this paper, in order to examine the relationships between the changes of the stiffness and damping of the impactor and vibrations of the dynamic characteristics of the impact model of a cantilevered beam with an impactor, impact force of the impactor and response characteristics of the cantilevered beam were analyzed by both numerical simulation and experiment. Since the stiffness and damping of the impactor have high nonlinear characteristics, the contact model using revised Herz-model was established by experiments. Also, the results of numerical analyses for dynamic response and impact force of a cantilevered beam with an impactor have a good agreement with experimental results.

• Steel and Composite Structures
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• v.7 no.6
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• pp.457-468
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• 2007

Analytical and experimental investigation on dynamic properties of extra lightweight concrete sandwich beams reinforced with various lay ups of carbon reinforced epoxy polymer composites (CFRP) are discussed. The lightweight concrete used in the core of the sandwich beams was made up of extra lightweight aggregate, Lica. The density of concrete was half of that of the ordinary concrete and its compressive strength was about $100Kg/cm^2$. Two extra lightweight unreinforced (control) beams and six extra lightweight sandwich beams with various lay ups of CFRP were clamped in one end and tested under an impact load. The dimension of the beams without considering any reinforcement was 20 cm ${\times}$ 10 cm ${\times}$ 1.4 m. These were selected to ensure that the effect of shear during the bending test would be minimized. Three other beams, made up of ordinary concrete reinforced with steel bars, were tested in the same conditions. For measuring the damping capacity of sandwich beams three methods, Logarithmic Decrement Analysis (LDA), Hilbert Transform Analysis (HTA) and Moving Block Analysis (MBA) were applied. The first two methods are in time domain and the last one is in frequency domain. A comparison between the damping capacity of the beams obtained from all three methods, shows that the damping capacity of the extra lightweight concrete decreases by adding the composite reinforced layers to the upper and lower sides of the beams, and becomes most similar to the damping of the ordinary beams. Also the results show that the stiffness of the extra lightweight concrete beams increases by adding the composite reinforced layer to their both sides and become similar to the ordinary beams.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.283-290
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• 2022

This study proposes a voltage control scheme in a synchronous reference frame to improve the dynamic characteristics of double-conversion UPSs. UPSs need to control positive and negative sequence voltage, so that positive and negative sequence extractors are generally used to obtain each sequence of the voltage and current. Voltage and current controllers for each sequence are implemented. However, the extractor causes considerable delay, and the delay restricts the control performance, especially for the current controller. To improve the dynamics of the current controller, the proposed scheme adopts a unified current controller without separating positive and negative sequences. By using discrete-time current controller, the control bandwidth can be extended significantly so that negative sequence current can be controlled. To enhance the performance, an additional feed-forward technique for output voltage regulation is proposed. The validity of the proposed controller is verified by experiments.

• The Journal of the Korea Contents Association
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• v.6 no.1
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• pp.54-63
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• 2006

In this paper we will propose a domain analysis methodology that uses an extended workflow mechanism based on dynamic modeling to solve problems of a traditional domain analysis on legacy systems. This methodology is called WODA(Workflow Oriented Domain Analysis). Following procedures on WODA, we can identify common/uncommon component, and also extract the cluster of components. It will be effectively reusable on developing new systems with these components. With our proposed component testing metrics, we can determine highly reusable component/scenario on identifying possible scenarios of the particular system. We can also recognize most critical/most frequent reusable components and prioritize possible component scenarios of the system. This paper contains one application of UPS that illustrates our autonomous modeling tool, WODA.

• Bulletin of the Society of Naval Architects of Korea
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• v.19 no.4
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• pp.53-59
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• 1982

Relative bow-motions of a ship in wave are investigated by using linear theory. The relative displacement is assumed to be composed of incident wave elevation, motion response, dynamic swell-up and ship wave elevation. Radiation problem is solved by distributing sources on the hull surface and wave elevation in a uniform stream is obtained by integrating Havelock's function with centerplane source distributions. Relative displacements for I.T.T.C. S7-175 model are calculated. Dynamic swell-ups make the relative displacement larger except small heading angles. Amplitudes of relative motion on weather-side are generally larger than those on lee-side. Ship wave elevations in a uniform stream also give considerable contributions and our calculations are verified to be reasonable in comparison with experimental results.